Depois de navegar um pouco na internet, parece bastante óbvio que o servidor VPN está bloqueando todas as solicitações de DNS que contenham a palavra "torrent", mesmo que seja uma torrente legal como torrent.ubuntu.com .
Eu tive alguns problemas para estabelecer uma conexão com um servidor VPN. Aqui está um link para o thread em questão: conexão VPN do StackExchange .
Foi principalmente uma questão de DNS e funciona agora. No entanto, agora posso resolver alguns nomes, mas não todos eles. Eu posso resolver www.google.com , mas não torrent.ubuntu.com por exemplo. Mesmo se eu usar o comando dig para especificar o DNS que desejo usar, não consigo resolver torrent.ubuntu.com enquanto estiver conectado à VPN. Quando não estou conectado à VPN, posso resolvê-lo e também posso resolvê-lo usando o DNS do meu servidor VPN.
Não conectado à VPN (84.200.69.80 é o endereço DNS fornecido pelo meu servidor VPN):
pi@raspberrypi:/etc/openvpn/vpnbook $ dig torrent.ubuntu.com
; <<>> DiG 9.9.5-9+deb8u10-Raspbian <<>> torrent.ubuntu.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 12612
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;torrent.ubuntu.com. IN A
;; ANSWER SECTION:
torrent.ubuntu.com. 600 IN A 91.189.95.21
;; Query time: 26 msec
;; SERVER: 194.168.4.100#53(194.168.4.100)
;; WHEN: Tue Mar 28 23:36:14 UTC 2017
;; MSG SIZE rcvd: 63
pi@raspberrypi:/etc/openvpn/vpnbook $ dig @8.8.8.8 torrent.ubuntu.com
; <<>> DiG 9.9.5-9+deb8u10-Raspbian <<>> @8.8.8.8 torrent.ubuntu.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 54658
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;torrent.ubuntu.com. IN A
;; ANSWER SECTION:
torrent.ubuntu.com. 565 IN A 91.189.95.21
;; Query time: 38 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Tue Mar 28 23:36:30 UTC 2017
;; MSG SIZE rcvd: 63
pi@raspberrypi:/etc/openvpn/vpnbook $ dig @84.200.69.80 torrent.ubuntu.com
; <<>> DiG 9.9.5-9+deb8u10-Raspbian <<>> @84.200.69.80 torrent.ubuntu.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 25789
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;torrent.ubuntu.com. IN A
;; ANSWER SECTION:
torrent.ubuntu.com. 153 IN A 91.189.95.21
;; AUTHORITY SECTION:
ubuntu.com. 600 IN NS ns4.p27.dynect.net.
ubuntu.com. 600 IN NS ns2.p27.dynect.net.
ubuntu.com. 600 IN NS ns1.p27.dynect.net.
ubuntu.com. 600 IN NS ns3.p27.dynect.net.
;; Query time: 48 msec
;; SERVER: 84.200.69.80#53(84.200.69.80)
;; WHEN: Tue Mar 28 23:36:47 UTC 2017
;; MSG SIZE rcvd: 149
Conectado à VPN:
pi@raspberrypi:/etc/openvpn/vpnbook $ dig torrent.ubuntu.com
; <<>> DiG 9.9.5-9+deb8u10-Raspbian <<>> torrent.ubuntu.com
;; global options: +cmd
;; connection timed out; no servers could be reached
pi@raspberrypi:/etc/openvpn/vpnbook $ dig @84.200.69.80 torrent.ubuntu.com
; <<>> DiG 9.9.5-9+deb8u10-Raspbian <<>> @84.200.69.80 torrent.ubuntu.com
; (1 server found)
;; global options: +cmd
;; connection timed out; no servers could be reached
pi@raspberrypi:/etc/openvpn/vpnbook $ dig @8.8.8.8 torrent.ubuntu.com
; <<>> DiG 9.9.5-9+deb8u10-Raspbian <<>> @8.8.8.8 torrent.ubuntu.com
; (1 server found)
;; global options: +cmd
;; connection timed out; no servers could be reached
pi@raspberrypi:/etc/openvpn/vpnbook $ dig www.google.com
; <<>> DiG 9.9.5-9+deb8u10-Raspbian <<>> www.google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 59828
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;www.google.com. IN A
;; ANSWER SECTION:
www.google.com. 132 IN A 172.217.20.196
;; Query time: 211 msec
;; SERVER: 84.200.69.80#53(84.200.69.80)
;; WHEN: Tue Mar 28 23:38:58 UTC 2017
;; MSG SIZE rcvd: 59